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RISS 인기검색어
- 검색키워드
- 저자 : Jinxin Gong (검색결과 4 건)
- 무료
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- 유료
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Effect of Viscous Damping Models on Displacement Ductility Demands for SDOF Systems
Zhibin Feng,Jinxin Gong 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.12
The viscous damping is a highly idealized but mathematically convenient way of representing the energy dissipation mechanisms not related to the hysteretic response. In this study, the tangent-stiffness proportional Rayleigh damping (TSPRD) appropriate for inelastic hysteretic structures outfitted with the supplemental damping devices is utilized in inelastic dynamic analysis of simple single-degree-of-freedom (SDOF) structures. A numerical procedure of dynamic equilibrium equation for SDOF systems with TSPRD model is derived for development of the general numerical solution scheme. By specifying various combinations of tangent-stiffness and mass proportional damping terms in TSPRD model, the influence of viscous damping models on displacement ductility demands is investigated. The results indicate that the difference in ductility demands for various damping models is considerable, depending on the periods of vibration, relative lateral strength, hysteretic models, stiffness deterioration and initial damping ratios. The constant-strength displacement ductility spectra, by considering both tangent-stiffness proportional and mass proportional damping, are developed in terms of site conditions, hysteretic rules and initial damping ratios.
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Evaluation of multi-lane transverse reduction factor under random vehicle load
Xiaoyan Yang,Jinxin Gong,Bohan Xu,Jichao Zhu 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.6
This paper presents the two-, three-, and four-lane transverse reduction factor based on FEA method, probability theory, and the recently actual traffic flow data. A total of 72 composite girder bridges with various spans, number of lanes, loading mode, and bridge type are analyzed with time-varying static load FEA method by ANSYS, and the probability models of vehicle load effects at arbitrary-time point are developed. Based on these probability models, in accordance to the principle of the same exceeding probability, the multi-lane transverse reduction factor of these composite girder bridges and the relationship between the multi-lane transverse reduction factor and the span of bridge are determined. Finally, the multi-lane transverse reduction factor obtained is compared with those from AASHTO LRFD, BS5400, JTG D60 or Eurocode. The results show that the vehicle load effect at arbitrary-time point follows lognormal distribution. The two-, three-, and four-lane transverse reduction factors calculated by using FEA method and probability respectively range between 0.781 and 1.027, 0.616 and 0.795, 0.468 and 0.645. Furthermore, a correlation between the FEA and AASHTO LRFD, BS5400, JTG D60 or Eurocode transverse reduction factors is made for composite girder bridges. For the two-, three-, and four-lane bridge cases, the Eurocode code underestimated the FEA transverse reduction factors by 27%, 25% and 13%, respectively. This underestimation is more pronounced in short-span bridges. The AASHTO LRFD, BS5400 and JTG D60 codes overestimated the FEA transverse reduction factors. The FEA results highlight the importance of considering span length in determining the multi-lane transverse reduction factors when designing two-lane or more composite girder bridges. This paper will assist bridge engineers in quantifying the adjustment factors used in analyzing and designing multi-lane composite girder bridges.
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Chloride Diffusivity of High-Performance Concrete due to Early-Age Shrinkage Cracking
Li-Na Ma,Yanhua Zhao,Jinxin Gong 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
Due to the addition of mineral admixtures, early-age shrinkage cracking is a common feature in high-performance concrete (HPC). Chloride diffusivity of HPC due to early-age shrinkage cracking was investigated through rapid chloride migration (RCM) method. Restrained/unrestrained slabs made of HPC containing fly ash (FA) and ground granulated blast-furnace slag (GGBS) were left outdoors for early-age shrinkage cracking, and then cylindrical samples were drilled from slabs for RCM test to quantify the chloride diffusion coefficient, wherein a crack influence factor was introduced to account for the contribution of cracking in the chloride diffusivity progress. Test results from unrestrained HPC reveal that the addition of mineral admixtures could densify the pore structure of HPC thus improved the chloride diffusion coefficient, though FA had a delayed effect. The RCM tests from restrained HPC indicate that the crack indeed had an effect on the chloride ion transportation, but pore structure still dominated the chloride ingress. For a fixed cement replacement, the more the GGBS in the mix, the higher the contribution of cracking to chloride ion penetration.
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Song Jin,Zhongcheng Li,Tianyun Lan,Zhanfa Dong,Jinxin Gong 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.3
Prestressed concrete containment vessel act as a reliable leak tight barrier during the accident conditions. There is a growing demand to study nonlinear behavior of containment structure under severe accident loads in depth. This paper presents nonlinear finite element analysis of prsestressed concrete containment vessel under severe accident loads with consideration of material nonlinearity, penetrations, local reinforcement and temperature-dependent degradationcharacteristic of materials. To reflect the prestressing effects realistically, non-uniform distribution of effective prestressing along the tendon profile is explicitly considered and python scripts are developed to add the corresponding temperature drop value for each node of the prestressed tendons to ABAQUS input files automatically. Nonlinear finite element analysis for pressure only case and combined thermal and pressure case has been investigated in detail. Nonlinear finite element analysis results of the containment structure indicate that, thermal effects have negligible effect on pressure capacity of containment, considering the thermal effects, pressure capacity of containment decrease not more than 5% and margin of the containment still meets the requirements of not less than 2.5. The effect of temperature exhibit significantly influence on displacement response of containment structure, and the effect of temperature on the strain of liner and reinforcing steel is much greater than that on prestressed tendon. Thermal effects exhibit the greatest influence on nonlinear displacement response of the dome apex location and the least influence on the 33 m elevation.
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